Powder washing apparatus



y 3, 1962 D. "r. KELLEY ETAL 3,033,133

POWDER WASHING APPARATUS Filed Sept. 26, 1955 INVENTORS gk 2 DEWITTT.KELLEY {9' ROGER S.BABCOCK EDWARD M. HOLUB Mair/h? ATTORNE ire StatesThis invention relates to powder washing, and more particularly toapparatus for the thermochemical removal of metal, or refractorysubstances of the sand type from metal bodies or structures, especiallycastings.

After a casting has been removed from the mold, loosely adherent sand isusually dislodged by mechanical shakers. Molding sand which sticks inpockets or crevices is later loosened with a pneumatic tool. The exactsequence of the cleaning procedure may vary; however, the next stepusually is to remove risers with a conventional oxygen cutting blowpipe.The casting may then be shotblasted to remove additional sand.

The riser cutting operation leaves a riser pad which itself must beremoved. The method selected to remove the riser pad depends upon itssize and location. Typical prior methods for removing riser pads are:grinding, chipping, machining, and oxygen scarfing.

Several types of grinders are in use. They can be classed as eitherportable grinders or swing grinders. General foundry practice requiresthe casting to be transported by overhead cranes to the grinders.

Pneumatic chipping is a method for removing fins, chaplets, chill nails,sand incrustations, and penetrations. As in the case of grinding, thecastings are moved from the cutting floor to an area where the chippersare located. All of such methods are time consuming and expensive. Thefoundrymen have had no relief from continually rising labor and overheadcosts and have, therefore, looked searchingly for ways of accomplishingcasting cleaning by quicker and less expensive methods.

Three types of oxygen working have been intermittently applied, withlittle success, to the casting cleaning problem, namely: oxygen scarfingwith or without powder; oxygen gouging; and conventional oxygen cuttingwith or without powder.

Oxygen scarfing, also called deseaming, involves a relatively largevolume stream of oxygen of relatively high velocity. The operationproceeds at a relatively high speed-40 feet per minute is an averagerate. A continuous, straigh-line pass is made, followed by successiveadjacent passes to remove a thickness of inch or more from the bodybeing processed. Such scarfing is best adapted to removing defectivesurfaces from billets or similar pieces which have a symmetricalcross-section and are of reasonable length. The included angle ofincidence of the nozzle axis to the surface plane is seldom greater than35 degrees. The scarfing process with or without powder has been used oncastings, but it is not well suited to this type work, because of therelatively small area of the riser pads, etc. Another reason is that itis impossible to change direction'because of the speed of the operation.This speed is a function of the cutting oxygen stream velocity which.isin the neighborhood of 900 feet per second. A further reason is thatthe scarfed surface is left with ridges between passes.

Oxygen gouging has also been applied to casting cleaning with littlesuccess. Oxygen gouging is best dilferentiated from scarfing by itsslower progressive speed and better directional control. Representativegouging speed is about 2 to 4 feet per minute as compared to 40 feet perminute for scarfing. Although gouging has not been very useful forcasting cleaning, it has found much favor in foundries for cleaning outcracks for subsequent welding ice repair. In an operation of this naturedefective material of variable depth and width must be removed. On theother hand, control of the cut is reduced when a very light cut is to bemade. Gouging provides good flexibility in making cuts of varying depthand for following irregular contours. This control is made possible bythe lowvelocity gouging oxygen stream which results from a restrictionor spud placed near the exit end of the gouging oxygen passage in thenozzle. As in the case of scarfing, the line of gouging action isstraight, except in those cases where reasonable deviation from astraight line is necessary. The included angle of incidence of thegouging oxygen stream to the plane of work surface is appreciably lessthan in the case of scarfing.

Conventional oxygen cutting with or without adjuvant powder is mostobviously unsuited to metal washing operations. This is due to the smallcross section and relatively high velocity of the cutting oxygen stream.An oxygen jet of this type is designed specifically for sever ingoperations. Here, the included angle of incidence of the cutting oxygenjet to the plane of workpiece surface is seldom less than 45 degrees. Itis usually normal to the surface and the nozzle is moved manually ormechanically in any desired direction over the workpiece. In some cases,a trimming cut is made after the riser is removed and during thetrimming cut the nozzle is frequently parallel to the casting surfacewhich remains after riser removal.

Thus, prior to the present invention-the problem of quickly andeconomically cleaning castings remained, to a large extent, unsolved.

The main object of this invention, therefore, is to provide means forthermochemically cleaning and conditioning the surfaces of ferrous metalcastings with substantial savings of time, labor and material comparedto the prior art. Another object is to provide novel apparatus forthermochemically washing metal castings that is effective, not only forremoving defects such as sand trapped or cast in the surfaces but, atthe same time, is also suitable for removing metal projections, orimperfections, from the castings. A further object is to provide apowder washing blowpipe that is efiicient in operation and easy tomanipulate. Other objects will appear from the following description.

According to the invention there is provided means for thethermochemical removal of metal and sand or the like from steel bodieswherein a relatively flat stream of finely divided powder, preferablyiron conveyed by air .at a velocity of 50-250 feet per second issuperimposed on a relatively low velocity (200-500 feet per second)round stream of oxygen, so that the exothermic burning of the ironpowder aids the oxidation of the base material of the area, As aresult,'slag does not accumulate on the adjacent areas, and the processis faster, more economical, and uses less powder than prior oxygenprocesses; it is faster and more economical than grinding; and provides,in some cases, the only way of reclaiming castings which have extensivepenetrations, thereby saving expensive castings which otherwise wouldhave to be scrapped.

The apparatus of the invention includes a portable blowpipe whichcomprises the combination of a tubular nozzle having a relatively largecentral passage for discharging a substantially round stream of oxygen,and a plurality of relatively small passages for discharging combustiblegas jets around such stream, with a separate relatively flat nozzlehaving a passage for discharging a substantially fiat stream ofair-borne adjuvant powder, and means connecting said nozzles in spacedrelation so that the extended longitudinal axes thereof form an acuteincluded angle in front of the nozzles, with the major transverse axisof the flat nozzle lying in a plane which is substantially at rightangles to a plane containing such longitudinal axis. The ratio of thewidth of the fiat powder discharge nozzle in the direction of such majortransverse axis to the diameter of the round oxygen discharge nozzleshould be kept within the limit of 1-3 to l for best results.

The blowpipe of the invention is highly suitable for all powder washingoperations such as removal of gate stubs, shifts or offsets, chill rodsand bars, reinforcing nails, burned-in sand, and penetrations (sand inmatrix of steel). It is particularly adaptable to medium size castingswhich require an appreciable amount of metal removal.

The invention includes the following general advantages:

(1) When applied to other than light fins, powder washing greatlyreduces fin chipping and grinding-a very real advantage in view of greatscarcity of trained chippers in foundries. (On light fins, powderwashing time is about the same as chipping time.)

(2) Powder washing either eliminates or minimizes pad grinding time.

(3) When applied to sand removal, powder washing reduces hours ofchipping to a matter of minutes.

(4) Because of the versatility of our powder-washing equipment, powderwashing can often be used on surfaces which are relatively inaccessibleto other methods of metal removal.

(5) With practice, powder washing frequently produces surfaces which areas smooth a the casting surface itself.

In the drawing:

FIG. 1 is a perspective view of powder washing blowpipe apparatus,illustrating the invention, in use;

FIG. 2 is a view in side elevation of a preferred powder washingblowpipe embodying the invention; and

FIG. 3 is a similar (fragmentary) view of a modification.

As shown in the drawing, blowpipe comprises a handle 12 at the back ofwhich are located an oxygen throttle valve 14 and an acetylene, or fuelgas, throttle valve 16, as well as a cutting oxygen valve 17 having alever 18 extending forwardly over such handle. A powder inlet tube 20extends alongside the handle 12 and leads to a powder valve 21 having anupwardly extending fingerpiece 22 located in front of the lever 18.Pipes 24, 26 and 28 conduct the air-borne powder, cutting oxygen, andoXy-acetylene mixture, respectively, forwardly to the head 30 of theblowpipe, which head is provided with a tubular nozzle 32 and a separateflat nozzle 34 having a divergent section as illustrated in FIG. 1. Suchnozzles are connected by a clamp 35.

The tubular nozzle 32 is bent toward the fiat nozzle 34, as shown, andhas a central passage from which a round stream of oxygen 36, FIG. 1, isdischarged when the lever 18 is moved toward the handle 12. Likewise, afiat stream of air-borne powder 38 is discharged from the nozzle 34 whenthe finger-piece 22 is operated. The nozzle 32 is also provided with anannular series of passages 40, surrounding the central passage 42, fordischarging a plurality of jets of oxy-acetylene (or oxy-fuel gas)flames 44 in the same general direction as the oxygen stream 36. In usethe blowpipe 10 is held in the manner of an automatic rifle or billiardcue.

As shown in FIG. 1, the process comprises applying at an acute includedangle against the surface 46 to be washed a round, gouging-velocitystream 36 of commercially pure oxygen which is surrounded by flames 44extending in the same general direction as such oxygen stream,simultaneously applying against such surface 46 at a somewhat greateracute included angle a fiat stream of air-borne powder 38 composedmainly of iron, and

manually swinging the blowpipe head 30 from side-toside and forwardly,thereby moving such streams and flames transversely back and forthacross such surface while advancing them along the surface in thegeneral direction or" such streams, as shown by the arrows 48. Theresulting thermochemical reaction with the material of the work W,cleans the surface by removing incrustations and other foreign mattertherefrom as a result of the combined melting and planing action of suchflames and oxygen and air-borne powder streams.

1..e oxygen gouging nozzle 32a may be straight and the powder nozzle 34amay be bent as shown in FIG. 3; or both nozzles may be bent, as desired,without departing from the invention.

The process of the invention is especially recommended for thefollowing:

(1) Fin washing where foundries must remove finlike projections fromlarge surface area steel castings. (Sand may or may not adhere to finsin fillet at junction with casting.)

(2) Pad washing which consists of removing stumps which remain oncastings after gates and risers have been cut away.

(3) Removal of defects in steel casings attributed to mold (includingcore) sand-for example, removal of sand blisters, sand inclusions, orsand penetrations. Defects and their causes are considered in detailimmediately below under separate heading. (The core is that portion of amold which produces hollow interiors within castings).

(4) Contour washing where it is necessary to smooth down the surface ofcastings and remove adhering particles of sand and scale.

(5) Washing of repair welds when necessary to remove excess weld metal.

Prior to the present invention the uses of adjuvant powder for scarfingor cutting carbon or alloy steels and cast iron were well established.Also, the application of low-velocity oxygen cutting as applied to rivetwashing or gouging operations were likewise common to industry. Theproblem therefore was one of combining the use of adjuvant powder withthe low-velocity gouging process. An unexpected result was that theaddition of powder solved the problem of making very shallow cuts withthe gouging process. Powder also added greatly to the control for suddenchanges of direction. Another result was that the heated slag and itsfiuxing action washed out more effectively troublesome sandincrustations and penetrations.

The next step was to determine how the powder should be introduced.Experimentation with internally-fed powder, that is powder suspended inand borne by the cutting oxygen, was found to be inefiicient becausedilution by the powder bearing air interfered with the cutting oxygenefficiency. The powder quickly eroded the cutting oxygen passage, andcontributed greatly to sintering difficulties on the inside surfaces ofthe cutting oxygen passage near the nozzle exit.

At this point it should be noted that a somewhat parallel problemexisted in powder scarfing wherein the solution was the superimpositionof the powder stream on the scarfing oxygen stream. It was concludedfrom past experience, however, that the combination of a slotted powdernozzle and a slotted scarfing nozzle could not be well adapted tocontrolled operation in all positions and in varying directions. Powderscarfing is done in the downhand position. It was therefore decided thata powder nozzle of circular cross section should be used with aconventional low-velocity gouging nozzle.

The results were encouraging but, because of an uneven reaction zone, ascalloped effect was produced on the finished surface. It was also foundthat sintering occurred in the gouging oxygen passage because of theclose proximity of the powder and oxygen discharge points which wasnecessary to obtain optimum conditions. It was further observed thatthere was too high a concentration of powder in the center of thereaction zone; this uneven distribution tended to cause erraticoperation. Nevertheless, there was indication that the apparatus couldbe operated in all positions as would be necessary in the cleaning of acasting. At this point, we discovered that the usual continuous,straight-line progression of the cutting action could be improved onwith a side-to-side motion. Such side-to-side weaving action relievedthe slag overlay problem and contributed to the efficiency of metalremoval.

In order to distribute the powder more evenly over the top of the oxygenstream, and to deposit an overlap of powder on each side to facilitatethe weaving motion, one of the circular powder tubes was formed into acrescent shape. The profile of this powder slot therefore conformed tothat of the top half of the oxygen stream.

A very pronounced improvement in flatness of scarf and efficiency overthat obtained with the round powder stream on round oxygen streamresulted. It next occurred to us that a crescent shaped powder tubewould be relatively expensive to manufacture. As a result, we tried aflat, slotted powder tube with even better results.

We have determined that the cutting oxygen flow should be 400 to 500c.f.h., the preheat acetylene and preheat oxygen flow should beapproximately 100-125 c.f.h. each, and the powder flow should be 1520lbs. per hour. The ferrous base powder should be free flowing and shouldpass through 100 mesh screen. Best results are obtained where ironpowders, Whose total iron content is 94-99 percent, are used. The widthof the slotted discharge passage in the direction of the majortransverse axis thereof should be no less than the diameter of the roundoxygen discharge passage, and no more than three times such diameter.Below such limits at side-tO-side washing motion is difficult tomaintain without a loss of the reaction. Above such limits powder iswasted with resultant excessive usage.

Powder washing, using the appartus described herein, is faster, moreeconomical, and uses less powder than other methods. It is faster andmore economical than grinding, and makes possible the reclamation ofcastings which have extensive penetrations and otherwise would have tobe scrapped.

This application is a continuation-in-part of our application Serial No.398,553, filed December 16, 1953, now

abandoned which is in turn a division of our application Serial No.266,388, filed January 14, 1952 now Patent No. 2,735.796.

We claim:

1. Portable blowpipe apparatus for manually thermochemically washingferrous metal castings with a side-toside motion across the width of thearea to be washed, comprising the combination of a tubular nozzle havinga round central passage for discharging a round stream of oxygen, and aplurality of relatively small passages for discharging combustible gasjets around such stream, with a separate nozzle having a single fiatpassage provided with a divergent section for discharging a fiat streamof evenly distributed gas-borne powder composed essentially of iron,means connecting said nozzles in spaced relation so that the extendedlongitudinal axes thereof form an acute included angle in front of thenozzles, with the major transverse axis of the powder nozzle lying in aplane which is substantially at right angles to a plane containing suchlongitudinal axes, and means for supplying oxygen at 400500 c.f.h. tosaid central passage and powder at 15-20 pounds/hour to said powdernozzle, the width of said flat powder discharge passage in the directionof the major transverse axis thereof being no less than the diameter ofsaid round oxygen discharge passage and no more than three times suchdiameter.

2. Blowpipe apparatus as defined by claim 1, in which at least one ofthe nozzles is bent.

3. A manual powder washing blowpipe comprising the combination with anoxy-acetylene gouging nozzle having an orifice adapted to discharge around stream of oxygen, and means for supplying oxygen thereto at a flowrate of 400-500 c.f.h. of an adiuvant powder nozzle mounted adiacentthereto and having a single flat passage provided with a divergentsection adapted to discharge a flat stream of uniformly distributedgas-borne powder at an acute included angle toward such oxygen stream,and means for supplying powder thereto at a flow rate of 15-20 poundsper hour, the width of said fiat powder discharge passage in thedirection of the major transverse axis thereof being no less than thediameter of said round oxygen discharge passage and no more than threetimes such diameter.

References Cited in the file of this patent UNITED STATES PATENTS2,622,048 Moesinger Dec. 16, 1952 2,627,826 Meincke Feb. 10, 19532,674,210 Holub et a1 Apr. 6, 1954

